Thanks for the reply. Update; I was able to remove the existing cap...it was rusted on. Next problem is that the diameter of the interior flue pipe is 4 3/8"-give or take. All of the replacement caps and/or roof jacks that I can find have an interior flue pipe diameter of 5 3/8". Is there ...

I am in the process of re-roofing a mobile home that contains Intertherm gas FAU model #MGH-055ABWL-07. The termination cap on the end of the flue is rusted out. Will Crown assembly #903656 work on this flue as a replacement? I cannot get the existing cap off...rusted? Or are there attachment screws...